Phone interview is fine- fairly standard questions about yourself and your motivations. A few days later I was asked to come in for an interview. The face-to-face interview was quite tough. Firstly, you are given a few lines of code in python, and have to suggest improvements which I found difficult, and there is also a maths/ probability section that I would have not been able to do if it weren't for my maths degree. Then you have to talk through all of your answers with the person and what you did wrong. Then there was a competency task which was fairly standard interview, and then a group project. I got the impression that the interviewers are more interested in how you learn and what your attitude is rather than what you know. Everyone there was really friendly to me, and I learned a lot.